I have a 08 marine master trailer under my triton. it has a single axle with disc surge brakes. I was pulling it the other day and my brakes got very hot and there was a lot of brake dust on my wheels. I pulled it home and took of the wheel and brake caliper and I could not get the piston on the calipers depressed. The acctuator on the tongue is working properly. has anyone had this happen before? what would cause this? Is this expensive to fix?